The original description for the Scepter of Fulmination before the description was corrected was this:

This scepter’s blast is so powerful it will daze opponents.

This suggests that it was originally planned for the weapon to daze opponents instead of slowing, but it was likely to have been changed because of how powerful this would be.

Although it may do noticeably less damage (150 damage and 5 targets) compared to the Scepter of Storms (300 damage and 5 targets) Fulmi is the only slowing scepter, meaning it is great in places like the Abyss and many dungeons in general because it can slow down any mob that tries to mug you. Even after the recent rebalance, it can be used as a primary scepter fairly well knowing how useful slow is to give you breathing room and let you land more shots.